At approximately the turn of the 20th century, excavating tools employed excavating teeth with replaceable ground engaging tips known as points. The points were connected to an adaptor attached to the shovel dipper, drag-line bucket or similar tool. An example is disclosed in U.S. Pat. No. 564,664. As the two part assembly became established practice, a number of methods evolved for joining the point to the adaptor. Depending on the conditions, a given adaptor would be re-equipped with 5 to 30 teeth or points to maintain a sharp penetrating edge during excavation. The ease of replacement of the point became important because it minimized the amount of wasted throw-away metal and also minimized the down time of the tool.
The assemblies used to attach a point to the adaptor consisted mainly of two designs, the wedge design and the pin design. In the wedge design, the point is joined to the adaptor by wedges hammered in place. One disadvantage of this method is the wedges would often become dislodged during use of the excavating tool. This design posed serious safety hazards to workers. To prevent this danger, the wedges were often tack-welded in place. However, removal of the wedges was then difficult and time consuming. Another disadvantage of this method is that the removal of the wedge required the drag-line bucket to be turned up on its front end in order to gain access to the wedge.
U.S. Pat. No. 3,256,622 describes a wedge pin assembly used to fasten a point to the adaptor. The wedge pin is received into an open-ended bore. The wedge pin is removed by being hammered through the slot with a specially designed hammer having a head size smaller than the bore size. The wedge pin is designed to cause interference in the bore but still be removable. One disadvantage of this arrangement is the tendency of the wedge to shatter or break during removal causing pieces to jam as well as dangering workers.
Another pin assembly is disclosed in Canadian Patent Application No. 2,121,993. This patent discloses a threaded pin and insert assembly to secure a point onto the adaptor. A threaded insert is placed into the adaptor pin opening. The point is then placed over the adaptor. A lock washer is concentrically placed over the pin opening on the point. The pin is screwed into the insert. Disadvantages of this assembly include the loosening of the pin from the insert while the point-adaptor assembly is in use, the cumbersome and relatively complex design, and the longer point replacement time as compared with more conventional teeth.
U.S. Pat. No. 3,410,010 describes a dipper tooth having a detent and key assembly inserted into a passage in the tooth and adaptor. A resilient retaining member is received into the adaptor. The member has a recess on its lower edge for receiving a metallic insert. The resilient retaining member and insert extend into a passage extending through the adaptor and point. A key having a notch in its upper surface is inserted into the passage. As the key enters the passage, its front end engages a recess in the lower surface of the passage to allow the key to travel past the insert. The key forces the insert upward, compressing the resilient member, until the insert engages the key notch. This arrangement has the disadvantage that when the tooth and adaptor are in use, the key may be repeatly jolted upward against the insert. This movement may compress the resilient member allowing the insert to disengage the notch on the key. In this manner, the key may fall out of the passage allowing the tooth to come off the adaptor and possibly causing injury to nearby workers. Further, the resilient member has a limited life and, as it loses its resilience, it will not be able to adequately maintain the insert in the key notch.
Locking devices are designed to minimize the down time of the equipment and increase the life of the point and adaptor. With the increase in awareness of worker safety, another important requirement of the point-adaptor assembly is safe and easy installation. The prior art devices do not satisfy these requirements and there therefore is a need for a locking device which is easy, safe, and fast to install and remove.